Electrochromic devices

ABSTRACT

Conventional electrochromic devices frequently suffer from poor reliability and poor performance. Improvements are made using entirely solid and inorganic materials. Electrochromic devices are fabricated by forming an ion conducting electronically insulating interfacial region that serves as an IC layer. In some methods, the interfacial region is formed after formation of an electrochromic and a counter electrode layer. The interfacial region contains an ion conducting electronically insulating material along with components of the electrochromic and/or the counter electrode layer. Materials and microstructure of the electrochromic devices provide improvements in performance and reliability over conventional devices.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is related to U.S. application Ser. No. 12/772,075,filed Apr. 30, 2010, entitled “Electrochromic Devices”, the content ofwhich is incorporated herein by reference in its entirety.

BACKGROUND

Electrochromism is a phenomenon in which a material exhibits areversible electrochemically-mediated change in an optical property whenplaced in a different electronic state, typically by being subjected toa voltage change. The optical property is typically one or more ofcolor, transmittance, absorbance, and reflectance. One well knownelectrochromic material, for example, is tungsten oxide (WO₃). Tungstenoxide is a cathodic electrochromic material in which a colorationtransition, transparent to blue, occurs by electrochemical reduction.

Electrochromic materials may be incorporated into, for example, windowsand mirrors. The color, transmittance, absorbance, and/or reflectance ofsuch windows and mirrors may be changed by inducing a change in theelectrochromic material. One well known application of electrochromicmaterials, for example, is the rear view mirror in some cars. In theseelectrochromic rear view mirrors, the reflectivity of the mirror changesat night so that the headlights of other vehicles are not distracting tothe driver.

While electrochromism was discovered in the 1960's, electrochromicdevices still unfortunately suffer various problems and have not begunto realize their full commercial potential. Advancements inelectrochromic technology, apparatus and related methods of makingand/or using them, are needed.

SUMMARY OF INVENTION

A typical electrochromic device includes an electrochromic (“EC”)electrode layer and a counter electrode (“CE”) layer, separated by anionically conductive (“IC”) layer that is highly conductive to ions andhighly resistive to electrons. In other words, the ionically conductivelayer permits transport of ions but blocks electronic current. Asconventionally understood, the ionically conductive layer thereforeprevents shorting between the electrochromic layer and the counterelectrode layer. The ionically conductive layer allows theelectrochromic and counter electrodes to hold a charge and therebymaintain their bleached or colored states. In conventionalelectrochromic devices, the components form a stack with the ionconducting layer sandwiched between the electrochromic electrode and thecounter electrode. The boundaries between these three stack componentsare defined by abrupt changes in composition and/or microstructure.Thus, the devices have three distinct layers with two abrupt interfaces.

Quite surprisingly, the inventors have discovered that high qualityelectrochromic devices can be fabricated without depositing an ionicallyconducting electrically insulating layer. In accordance with certainembodiments, the counter electrode and electrochromic electrodes areformed immediately adjacent one another, often in direct contact,without separately depositing an ionically conducting layer. It isbelieved that various fabrication processes and/or physical or chemicalmechanisms produce an interfacial region between contactingelectrochromic and counter electrode layers, and this interfacial regionserves at least some functions of an ionically conductive electronicallyinsulating layer in conventional devices. Certain mechanisms that may bekey to forming the interfacial region are described below.

The interfacial region typically, though not necessarily, has aheterogeneous structure that includes at least two discrete componentsrepresented by different phases and/or compositions. Further, theinterfacial region may include a gradient in these two or more discretecomponents. The gradient may provide, for example, a variablecomposition, microstructure, resistivity, dopant concentration (forexample, oxygen concentration), and/or stoichiometry.

In addition to the above discoveries, the inventors have observed thatin order to improve device reliability, two layers of an electrochromicdevice, the electrochromic (EC) layer and the counter electrode (CE)layer, can each be fabricated to include defined amounts of lithium.Additionally, careful choice of materials and morphology and/ormicrostructure of some components of the electrochromic device providesimprovements in performance and reliability. In some embodiments, alllayers of the device are entirely solid and inorganic.

Consistent with above observations and discoveries, the inventors havediscovered that formation of the EC-IC-CE stack need not be done in theconventional sequence, EC→IC→CE or CE→IC→EC, but rather an ionconducting electronically insulating region, serving as an IC layer, canbe formed after formation of the electrochromic layer and the counterelectrode layer. That is, the EC-CE (or CE-EC) stack is formed first,then an interfacial region serving some purposes of an IC layer isformed between the EC and CE layers using components of one or both ofthe EC and CE layers at the interface of the layers. Methods of theinvention not only reduce fabrication complexity and expense byeliminating one or more process steps, but provide devices showingimproved performance characteristics.

Thus, one aspect of the invention is a method of fabricating anelectrochromic device, the method including: forming an electrochromiclayer including an electrochromic material; forming a counter electrodelayer in contact with the electrochromic layer without first providingan ion conducting electronically insulating layer between theelectrochromic layer and the counter electrode layer; and forming aninterfacial region between the electrochromic layer and the counterelectrode layer, wherein said interfacial region is substantially ionconducting and substantially electronically insulating. Theelectrochromic layer and counter electrode layer are typically, but notnecessarily, made of one or more materials that are more electronicallyconductive than the interfacial region but may have some electronicallyresistive character. The interfacial region can contain componentmaterials of the EC layer and/or the CE layer, and in some embodiments,the EC and CE layers contain component materials of the interfacialregion. In one embodiment, the electrochromic layer includes WO₃. Insome embodiments, the EC layer includes WO₃, the CE layer includesnickel tungsten oxide (NiWO), and the IC layer includes lithiumtungstate (Li₂WO₄).

Heating may be applied during deposition of at least a portion of theelectrochromic layer. In one embodiment, where the EC layer includesWO₃, heating is applied after each of a series of depositions viasputtering in order to form an EC layer with a substantiallypolycrystalline microstructure. In one embodiment, the electrochromiclayer is between about 300 nm and about 600 nm thick, but the thicknessmay vary depending upon the desired outcome which contemplates formationof the interfacial region after deposition of the EC-CE stack. In someembodiments, the WO₃ is substantially polycrystalline. In someembodiments, an oxygen rich layer of WO₃ can be used as a precursor tothe interfacial region. In other embodiments the WO₃ layer is a gradedlayer with varying concentrations of oxygen in the layer. In someembodiments, lithium is a preferred ion species for driving theelectrochromic transitions, and stack or layer lithiation protocols aredescribed. Specifics of the formation parameters and layercharacteristics are described in more detail below.

Another aspect of the invention is a method of fabricating anelectrochromic device, the method including: (a) forming either anelectrochromic layer including an electrochromic material or a counterelectrode layer including a counter electrode material; (b) forming anintermediate layer over the electrochromic layer or the counterelectrode layer, where the intermediate layer includes an oxygen richform of at least one of the electrochromic material, the counterelectrode material and an additional material, where the additionalmaterial includes distinct electrochromic and/or counter electrodematerial, the intermediate layer not substantially electronicallyinsulating; (c) forming the other of the electrochromic layer and thecounter electrode layer; and (d) allowing at least a portion of theintermediate layer to become substantially electronically insulating andsubstantially ion conducting. Specifics of the formation parameters andlayer characteristics for this method are also described in more detailbelow.

Another aspect of the invention is an apparatus for fabricating anelectrochromic device, including: an integrated deposition systemincluding: (i) a first deposition station containing a material sourceconfigured to deposit an electrochromic layer including anelectrochromic material; and (ii) a second deposition station configuredto deposit a counter electrode layer including a counter electrodematerial; and a controller containing program instructions for passingthe substrate through the first and second deposition stations in amanner that sequentially deposits a stack on the substrate, the stackhaving an intermediate layer sandwiched in between the electrochromiclayer and the counter electrode layer; wherein either or both of thefirst deposition station and the second deposition station are alsoconfigured to deposit the intermediate layer over the electrochromiclayer or the counter electrode layer, and where the intermediate layerincludes an oxygen rich form of the electrochromic material or thecounter electrode material and where the first and second depositionstations are interconnected in series and operable to pass a substratefrom one station to the next without exposing the substrate to anexternal environment. In one embodiment, apparatus of the invention areoperable to pass the substrate from one station to the next withoutbreaking vacuum and may include one or more lithiation stations operableto deposit lithium from a lithium-containing material source on one ormore layers of the electrochromic device. In one embodiment, apparatusof the invention are operable to deposit the electrochromic stack on anarchitectural glass substrate. Apparatus of the invention need not havea separate target for fabrication of an ion conducting layer.

Another aspect of the invention is an electrochromic device including:(a) an electrochromic layer including an electrochromic material; (b) acounter electrode layer including a counter electrode material; and (c)an interfacial region between the electrochromic layer and the counterelectrode layer, wherein the interfacial region includes anelectronically insulating ion conducting material and at least one ofthe electrochromic material, the counter electrode material and anadditional material, where the additional material includes distinctelectrochromic and/or counter electrode material. In some embodimentsthe additional material is not included; in these embodiments theinterfacial region includes at least one of the electrochromic materialand the counter electrode material. Variations in the composition andmorphology and/or microstructure of the interfacial region are describedin more detail herein. Electrochromic devices described herein can beincorporated into windows, in one embodiment, architectural glass scalewindows.

These and other features and advantages of the invention will bedescribed in further detail below, with reference to the associateddrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The following detailed description can be more fully understood whenconsidered in conjunction with the drawings in which:

FIG. 1A is a schematic cross-section depicting conventional formation ofan electrochromic device stack.

FIG. 1B is a graph showing composition of EC, IC and CE layers in aconventional electrochromic stack.

FIGS. 2A-C are graphs showing representative component compositions forelectrochromic devices of the invention.

FIGS. 3A and 3B are process flows in accord with embodiments of theinvention.

FIGS. 4A-4C are schematic cross-sections depicting formation ofelectrochromic devices in accord with specific embodiments of theinvention.

FIG. 5 depicts an integrated deposition system of the invention in aperspective view.

FIG. 6 is a graph showing how process parameters and endpoint readoutscorrelate during formation of an electrochromic stack in accord withembodiments of the invention.

FIGS. 7 and 8A-C are actual cross-sections of electrochromic devicesmade using methods in accord with embodiments of the invention.

DETAILED DESCRIPTION

FIG. 1A is a schematic cross-section depicting a conventionalelectrochromic device stack, 100. Electrochromic device 100 includes asubstrate 102, a conductive layer (CL) 104, an electrochromic (EC) layer106, an ion conducting (IC) layer 108, a counter electrode (CE) layer110, and a conductive layer (CL) 112. Elements 104, 106, 108, 110, and112 are collectively referred to as an electrochromic stack 114.Typically, the CL layers are made of a transparent conductive oxide, andare commonly referred to as “TCO” layers. Since the TCO layers aretransparent, the coloring behavior of the EC-IC-CE stack is observablethrough the TCO layers, for example, allowing use of such devices on awindow for reversible shading. A voltage source 116, operable to applyan electric potential across electrochromic stack 114, effects thetransition of the electrochromic device from, for example, a bleachedstate (i.e., transparent) to a colored state. The order of the layersmay be reversed with respect to the substrate. That is, the layers canbe in the following order: substrate, transparent conductive layer,counter electrode layer, ion conducting layer, electrochromic materiallayer and (another) transparent conductive layer.

Again referring to FIG. 1A, in conventional methods of fabricating anelectrochromic stack, the individual layers are deposited one atop theother in a sequential format as depicted in the schematic on the leftside of FIG. 1A. That is, TCO layer 104 is deposited on substrate 102.Then EC layer 106 is deposited on TCO 104. Then IC layer 108 isdeposited on EC layer 106, followed by deposition of CE layer 110 on IClayer 108, and finally TCO layer 112 on CE layer 110 to formelectrochromic device 100. Of course, the order of steps can be reversedto make an “inverted” stack, but the point is that in conventionalmethods the IC layer is necessarily deposited on the EC layer followedby deposition of the CE layer on the IC layer, or the IC layer isdeposited on the CE layer followed by deposition of the EC layer on theIC layer. The transitions between the layers of material in the stackare abrupt.

One notable challenge with above procedure is the processing required toform the IC layer. In some prior approaches it is formed by a sol gelprocess which is difficult to integrate into a CVD or PVD processemployed to form the EC and CE layers. Further, IC layers produced bysol gel and other liquid-based processes are prone to defects thatreduce the quality of the device and may need to be removed by, forexample, scribing. In other approaches, the IC layer is deposited by PVDfrom a ceramic target, which can be difficult to fabricate and use.

FIG. 1B is a graph depicting material % composition versus position inthe electrochromic stack of FIG. 1A, namely layers 106, 108 and 110,that is, the EC, IC and CE layers. As mentioned, in conventionalelectrochromic stacks, the transitions between the layers of material inthe stack are abrupt. For example, EC material 106 is deposited as adistinct layer with little or no compositional bleed over to theadjacent IC layer. Similarly, IC material 108 and CE material 110 arecompositionally distinct with little or no bleed over to adjacentlayers. Thus, the materials are substantially homogeneous (except forcertain compositions of CE material described below) with abruptinterfaces. Conventional wisdom was that each of the three layers shouldbe laid down as distinct, uniformly deposited and smooth layers to forma stack. The interface between each layer should be “clean” where thereis little intermixing of materials from each layer at the interface.

One of ordinary skill in the art would recognize that FIG. 1B is anidealized depiction, and that in a practical sense there is inevitablysome degree of material mixing at layer interfaces. The point is, inconventional fabrication methods any such mixing is unintentional andminimal. The inventors have found that interfacial regions serving as IClayers can be formed where the interfacial region includes significantquantities of one or more electrochromic and/or counter electrodematerials by design. This is a radical departure from conventionalfabrication methods.

As mentioned above, the inventors have discovered that formation of theEC-IC-CE stack need not be conducted in the conventional sequence,EC→IC→CE or CE→IC→EC, but rather an interfacial region serving as theion conducting layer can be formed after deposition of theelectrochromic layer and the counter electrode layer. That is, the EC-CE(or CE-EC) stack is formed first, then an interfacial region, which maypossess at least some functions of an IC layer, is formed between the ECand CE layers using components of one or both of the layers (and oranother electrochromic or counter electrode material in someembodiments) at the interface of the layers. The interfacial regionserves at least some function of a conventional IC layer because it issubstantially ion conducting and substantially electronicallyinsulating. It should be noted, however, that interfacial regions asdescribed can have higher than conventionally accepted leakage currentsbut the devices show good performance nonetheless.

In one embodiment the electrochromic layer is formed with an oxygen richregion which is converted to the interfacial region or layer serving asan IC layer upon subsequent processing after the counter electrode layeris deposited. In some embodiments, a distinct layer which includes anoxygen rich version of an electrochromic material is used to(ultimately) form an interfacial layer serving as an IC layer betweenthe EC and CE layers. In other embodiments, a distinct layer whichincludes an oxygen rich version of a counter electrode material is usedto (ultimately) form an interfacial region serving as an IC layerbetween the EC and CE layers. All or a portion of the oxygen rich CElayer is converted to the interfacial region. In yet other embodiments,a distinct layer which includes an oxygen rich version of a counterelectrode material and an oxygen rich form of an electrochromic materialis used to (ultimately) form an interfacial region serving as an IClayer between the EC and CE layers. In other words, some or all ofoxygen rich material serves as a precursor to the interfacial regionthat serves as an IC layer. Methods of the invention can not only reduceprocess steps, but produce electrochromic devices showing improvedperformance characteristics.

As mentioned, it is believed that some of the EC and/or CE layer in aninterfacial region is converted to a material that provides one or morefunctions of an IC layer, notably high conductivity for ions and highresistivity for electrons. The IC functional material in the interfacialregion may be, for example, a salt of the conductive cations; forexample, a lithium salt.

FIGS. 2A, 2B and 2C show composition graphs of three possible examplesof electrochromic device stacks (each containing an EC layer, a CE layerand an interfacial region serving as an IC layer), where the EC materialis tungsten oxide (denoted here as WO₃, but meant to include WO_(x),where x is between about 2.7 and about 3.5, in one embodiment x isbetween about 2.7 and about 2.9), the CE material is nickel tungstenoxide (NiWO) and the interfacial region primarily comprises lithiumtungstate (denoted here as Li₂WO₄, in another embodiment, theinterfacial region is a nanocomposite of between about 0.5 and about 50(atomic) % Li₂O, between about 5 and about 95% Li₂WO₄, and about 5 andabout 70% WO₃) with some amount of the EC and/or the CE material. Inmore general terms, the interfacial region typically, though notnecessarily, has a heterogeneous structure that includes at least twodiscrete components represented by different phases and/or compositions,which phases or compositions vary in concentration over the width of theinterfacial region. Because of this the interfacial region that servesas an IC layer is sometimes referred to herein as a “gradient region,” a“heterogeneous IC layer” or a “dispersed IC layer.” The illustrations inFIGS. 2A, 2B and 2C, although described in terms of specific materials,are more generally representative of composition variations of anysuitable materials for electrochromic devices of the invention.

FIG. 2A depicts an electrochromic stack of the invention where the ECmaterial is a significant component of the interfacial region thatfunctions as an IC layer, while the CE material is not a significantcomponent. Referring to FIG. 2A, starting at the origin and moving fromleft to right along the x-axis, one can see that a portion the ECmaterial, WO₃, which is substantially all tungsten oxide, serves as theEC layer. There is a transition into the interfacial region where thereis gradually less tungsten oxide and correspondingly gradually more oflithium tungstate, up to and including near the end of the interfacialregion where there is a portion that is substantially all lithiumtungstate with some minor amounts of tungsten oxide. Although thetransition from the EC layer to the interfacial region is demarked at acomposition of substantially all tungsten oxide and de minimus amountsof lithium tungstate, it is clear that the transition is not abrupt asin conventional devices. In this example, effectively the transitionbegins to occur where the composition has sufficient quantity of lithiumtungstate to enable the material to serve at least some functions of anIC layer, for example, ion conduction and electronic insulation.Certainly the composition much closer to the CE layer, where thecomposition is substantially lithium tungstate, serves the function ofan IC layer, as lithium tungstate is known to exhibit these properties.But there is also some IC layer function in other parts of interfacialregion. The inventors have found that such “heterogeneous IC layers”improve switching characteristics and perhaps thermal cycling stabilityof electrochromic devices as compared to conventional devices withabrupt transitions. The CE layer in this example contains primarilynickel tungsten oxide as the active material, and has a relativelyabrupt transition to the nickel tungsten oxide composition at the edgeof the interfacial region. Methods for making stacks with suchinterfacial regions are described in more detail below.

It should be noted that, for example, that the nickel tungsten oxide CElayer in FIG. 2A is depicted as having about 20% lithium tungstate.Without wishing to be bound by theory, it is believed that the nickeltungsten oxide CE layer exists as nickel oxide cores or particlessurrounded by a shell or matrix of lithium tungstate which impartsmoderately good ionic conductivity to the CE layer, and thereby aids inthe electrochromic transition of the CE layer during operation of theelectrochromic stack. The exact stoichiometry of lithium tungstate inthe CE layer may vary significantly from embodiment to embodiment. Insome embodiments, there may also be some tungsten oxide in the CE layer.Also, because lithium ions travel to and from the EC and CE layers viathe interfacial region serving as the IC layer, there may be significantamounts of lithium tungstate in the EC layer, for example as depicted inFIG. 2A.

FIG. 2B depicts an electrochromic stack of the invention where the CEmaterial is a significant component of the interfacial region thatfunctions as an IC layer, while the EC material is not a significantcomponent. Referring to FIG. 2B, starting at the origin and moving fromleft to right along the x-axis, one can see that in this case, the ECmaterial, which is substantially all tungsten oxide, serves as the EClayer. There is an abrupt transition into the interfacial region wherethere is little if any tungsten oxide, but there is a large amount oflithium tungstate and at least some nickel tungsten oxide (CE material).The composition of the interfacial region changes along the x-axis withprogressively less and less lithium tungstate and correspondingly moreand more nickel tungsten oxide. The transition from the interfacialregion to the CE layer is demarked arbitrarily at a composition of about80% nickel tungsten oxide and about 20% of lithium tungstate, but thisis merely an example of where the transition occurs in a gradedcomposition. The interfacial region may be viewed as ending when no, orlittle, additional change in composition occurs when progressing furtherthrough the stack. In addition, the transition effectively ends wherethe composition has sufficient quantity of nickel tungsten oxide suchthat the material no longer serves at least some function that adistinct IC layer would serve. Certainly the composition much closer tothe CE layer as demarked, where the composition is 80% nickel tungstenoxide, serves the function of a CE layer. Likewise, the composition ofthe interfacial region much closer to the EC layer, where lithiumtungstate is the substantial component, serves as an ion conductingelectronically insulating material.

FIG. 2C depicts an electrochromic stack of the invention where both theEC material and the CE material are significant components of theinterfacial region that functions as an IC layer. Referring to FIG. 2C,starting at the origin and moving from left to right along the x-axis,one can see that a portion the EC material, WO₃, which is substantiallyall tungsten oxide, serves as the EC layer. There is a transition intothe interfacial region where there is gradually less tungsten oxide andcorrespondingly gradually more lithium tungstate. In this example, abouta third of the way through what is demarked as the interfacial region,there is also a growing amount of nickel tungsten oxide counterelectrode material. At about midway through what is demarked as theinterfacial region, there is about 10% each of tungsten oxide and nickeltungsten oxide and 80% lithium tungstate. In this example there is noabrupt transition between an EC layer and an IC layer or between an IClayer and a CE layer, but rather an interfacial region which has acontinuous graded composition of both the CE and EC materials. In thisexample, the lithium tungstate component peaks at about half way throughthe interfacial region, and so this region is likely the strongestelectronically insulating portion of the interfacial region.

As mentioned above in the Summary of Invention, the EC and CE layers mayinclude material components that impart some electrical resistivity tothe EC and CE layers; the lithium tungstate in described in FIGS. 2A-Cthat spans all three regions, at least in some quantity, is an exampleof such materials that impart electrical resistivity to the EC and CElayers.

FIGS. 2A-C represent only three non-limiting examples of gradedcompositions of interfacial regions that serve as IC layers inelectrochromic devices of the invention. One of ordinary skill in theart would appreciate that many variations are possible without escapingthe scope of the invention. In each of the examples in FIGS. 2A-C thereis at least one layer where there are only two material components andone of the components is de minimus. The invention is not limited inthis way. Thus, one embodiment of the invention is an electrochromicdevice including a electrochromic layer, an interfacial region servingas an IC layer, and a counter electrode layer, wherein at least onematerial component of each of the aforementioned two layers and oneregion of the device is present in each of the electrochromic layer, theinterfacial region and the counter electrode layer in at least about 25%by weight, in another embodiment at least about 15% by weight, inanother embodiment at least about 10% by weight, in another embodimentat least about 5% by weight, in yet another embodiment at least about 2%by weight.

The amount of electrochromic and/or counter electrode material in theinterfacial region can be significant, in one embodiment as much as 50%by weight of the interfacial region. However, in many embodiments, theion-conducting electrically-insulating material is typically themajority component, while the remainder of the interfacial region iselectrochromic and/or counter electrode material. In one embodiment, theinterfacial region includes between about 60% by weight and about 95% byweight of the ion-conducting electrically-insulating material while theremainder of the interfacial region is electrochromic and/or counterelectrode material. In one embodiment, the interfacial region includesbetween about 70% by weight and about 95% by weight of theion-conducting electrically-insulating material while the remainder ofthe interfacial region is electrochromic and/or counter electrodematerial. In one embodiment, the interfacial region includes betweenabout 80% by weight and about 95% by weight of the ion-conductingelectrically-insulating material while the remainder of the interfacialregion is electrochromic and/or counter electrode material.

In some embodiments, interfacial regions in devices described herein maybe relatively distinct, that is, when analyzed, for example bymicroscopy, there are relatively distinguishable boundaries at adjoininglayers, even though the interfacial region contains amounts of theelectrochromic and/or counter electrode material. In such embodiments athe interfacial region's thickness can be measured. In embodiments wherethe interfacial region is formed from an oxygen-rich(super-stoichiometric) region of an EC and/or CE layer, the ratio of thethickness of the interfacial region as compared to the layer or layersit is formed from is one metric for characterizing the interfacialregion. For example, an electrochromic layer is deposited with anoxygen-rich upper layer. The EC layer may include a single metal oxideor two or more metal oxides mixed homogenously or heterogeneously inlayers or more diffuse regions. The EC layer is 550 nm thick, includingthe oxygen-rich layer (or region). If about 150 nm of the EC layer isconverted to interfacial region, then about 27% of the EC is convertedto interfacial region, that is, 150 nm divided by 550 nm. In anotherexample, the EC layer includes a first metal oxide region (or layer) anda second metal oxide layer (or region) that is oxygen-rich. If all or aportion of the oxygen-rich metal oxide layer is converted to interfacialregion, then the thickness of the interfacial region divided by thetotal thickness of the first and second metal oxide layers (prior toformation of the interfacial region) is a metric for the interfacialregion. In one embodiment, the interfacial region includes between about0.5% and about 50% by thickness of a precursor region (EC and/or CE,including oxygen-rich portion) used to form it, in another embodiment,between about 1% and about 30%, in yet another embodiment, between about2% and about 10%, and in another embodiment between about 3% and about7%.

The inventors have discovered that graded compositions serving as the IClayer have many benefits. While not wishing to be bound by theory, it isbelieved that by having such graded regions, the efficiency of theelectrochromic transitions is improved dramatically. There are otherbenefits as described in more detail below.

While not wishing to be bound to theory, it is believed that one or moreof the following mechanisms may affect the transformation of EC and/orCE material to an IC functioning material in the interfacial region.However, the performance or application of the invention is not limitedto any of these mechanisms. Each of these mechanisms is consistent witha process in which IC layer material is never deposited duringfabrication of the stack. As is made clear elsewhere herein, apparatusof the invention need not have a separate target comprising material foran IC layer.

In a first mechanism, the direct lithiation of the electrochromicmaterial or the counter electrode material produces an IC material (forexample, a lithium tungstate) in the interfacial region. As explainedmore fully below various embodiments employ direct lithiation of one ofthe active layers at a point in the fabrication process between theformation of the EC and CE layers. This operation involves exposure ofthe EC or CE layer (whichever is formed first) to lithium. According tothis mechanism, a flux of lithium passing through the EC or CE layerproduces an ionically conductive, electronically resistive material suchas a lithium salt. Heating or other energy can be applied to drive thisflux of lithium. This described mechanism converts the top or exposedportion of the first formed layer (EC or CE layer) prior to formation ofthe second layer (CE or EC layer).

In a second mechanism, lithium diffusing from one of the EC or CE to theother layer, after both layers have formed and/or during formation of asecond layer upon a lithiated first layer, causes conversion of part ofone of the EC and/or CE at their interface to the interfacial regionhaving the IC functioning material. The lithium diffusion may take placeafter all the second layer has formed or after only some fraction of thesecond layer has formed. Further, the diffusion of lithium andconsequent conversion to IC functional material take place in either thefirst or second deposited layers and in either the EC or CE layer. Inone example, the EC layer is formed first and then lithiated. As the CElayer is subsequently deposited on top of the EC layer, some lithiumdiffuses from the underlying EC layer toward and/or into the CE layercausing a transformation to an interfacial region which contains an ICfunctioning material. In another example, the EC layer formed first(optionally with an oxygen rich upper region), then the CE layer isformed and lithiated. Subsequently some lithium from the CE layerdiffuses into the EC layer where it forms the interfacial region havingthe IC functioning material. In yet another example, the EC layer isdeposited first and then lithiated to produce some IC functioningmaterial according to first the mechanism described above. Then, whenthe CE layer is formed, some lithium diffuses from the underlying EClayer toward the CE layer to produce some IC material in an interfacialregion of the CE layer. In this manner, the IC functioning materialnominally resides in both the CE and EC layers proximate theirinterface.

In a third mechanism, the EC and CE layers are formed to completion (orat least to the point where the second formed layer is partiallycomplete). Then, the device structure is heated and the heating convertsat least some of the material in the interfacial region to an ICfunctioning material (for example, a lithium salt). Heating, for exampleas part of a multistep thermochemical conditioning (MTCC) as describedfurther herein, may be performed during deposition or after depositionis completed. In one embodiment, the heating is performed after atransparent conductive oxide is formed on the stack. In anotherembodiment, heating is applied after the second layer is partially orwholly complete, but before a transparent conductive oxide is appliedthereto. In some cases, the heating is directly and primarilyresponsible for the transformation. In other cases, the heatingprimarily facilitates the diffusion or flux of lithium ions that createsthe IC-functioning material region as described in the second mechanism.

Finally, in a fourth mechanism, current flowing between the EC and CElayers drives the transformation of at least one of the electrochromicmaterial and the counter electrode material to the IC-functioningmaterial in the interfacial region. This may occur because, for example,an ion flux associated with the flowing current is so large it drives achemical transformation of EC and/or CE material to IC material in theinterfacial region. For example, as explained below, a large lithiumflux through tungsten oxide in an EC layer may produce lithiumtungstate, which serves as an IC material. The lithium flux may beintroduced during, for example, an initial activation cycle of a newlyformed device. However, this need not be the case, as otheropportunities for driving high ionic fluxes may be more appropriate foreffecting the conversion. Methods of the invention can be performed byone of ordinary skill in the art without resort to any one or more ofthe above mechanisms.

FIG. 3A is a process flow, 300, in accord with methods of the invention.Specifically, an EC layer is deposited (on a CL, for example a TCO), see305. Then a CE layer is deposited, see 310. After the EC and CE layersare deposited, then an interfacial region serving as an IC layer isformed therebetween, see 315. One embodiment of the invention is ananalogous method (not depicted) where steps 305 and 310 are reversed.The thrust of the method being that the interfacial region, functioningas an IC layer, is formed after the EC and CE layers, in someembodiments using at least part of one of the EC and CE layers to makethe interfacial region. For this reason, interfacial regions formed inthis way are sometimes referred to as “intrinsic” IC layers. In otherembodiments a distinct layer is formed between the EC and CE layers, forexample using an oxygen-enriched version of the EC material or the CEmaterial, where the layer is converted whole or in part to theinterfacial region, but again, after formation of the EC and CE layers.Various methods to form the interfacial region after the EC-CE stack isformed are described below.

Thus, as mentioned, one aspect of the invention is a method offabricating an electrochromic device, the method including: forming anelectrochromic layer including an electrochromic material; forming acounter electrode layer in contact with the electrochromic layer withoutfirst providing an ion conducting electronically insulating layerbetween the electrochromic layer and the counter electrode layer,wherein the counter electrode layer includes a counter electrodematerial; and forming an interfacial region between the electrochromiclayer and the counter electrode layer, wherein said interfacial regionis substantially ion conducting and substantially electronicallyinsulating. The interfacial region can contain component materials ofthe EC layer, the CE layer or both. The interfacial region can be formedin a number of ways, as described in more detail below.

FIG. 3B is a process flow, 320, showing a process flow in accord withthe method described in relation to FIG. 3A, in particular, a processflow for depositing an EC layer, then a CE layer and ultimately formingan interfacial region, functioning as an IC layer therebetween. Evenmore particularly, in this embodiment, the EC layer includes WO₃ withvarious amounts of oxygen, in particular compositions andconfigurations; the CE layer includes NiWO, the interfacial regionincludes Li₂WO₄, and TCO materials such as indium tin oxide andfluorinated tin oxide are used. It should be noted that the layers ofthe electrochromic devices are described below in terms of solid statematerials. Solid state materials are desirable because of reliability,consistent characteristics and process parameters and deviceperformance. Exemplary solid state electrochromic devices, methods andapparatus for making them and methods of making electrochromic windowswith such devices are described in U.S. Non-provisional patentapplication Ser. No. 12/645,111, entitled “Fabrication of LowDefectivity Electrochromic Devices,” by Kozlowski et al., and U.S.Non-provisional patent application Ser. No. 12/645,159, entitled“Electrochromic Devices,” by Wang et al., both of which are incorporatedby reference herein for all purposes. In particular embodiments, theelectrochromic devices of the invention are all solid state and made inapparatus that allow deposition of one or more layers of the stack in acontrolled ambient environment. That is, in apparatus where the layersare deposited without leaving the apparatus and without, for example,breaking vacuum between deposition steps, thereby reducing contaminantsand ultimately device performance. In a particular embodiment, apparatusof the invention do not require a separate target for depositing an IClayer, as is required in conventional apparatus. As one of ordinaryskill in the art would appreciate, the invention is not limited to thesematerials and methods, however, in certain embodiments, all of thematerials making up electrochromic stacks and precursor stacks (asdescribed below) are inorganic, solid (i.e., in the solid state), orboth inorganic and solid.

Because organic materials tend to degrade over time, for example whenexposed to ultraviolet light and heat associated with windowapplications, inorganic materials offer the advantage of a reliableelectrochromic stack that can function for extended periods of time.Materials in the solid state also offer the advantage of not havingcontainment and leakage issues, as materials in the liquid state oftendo. It should be understood that any one or more of the layers in thestack may contain some amount of organic material, but in manyimplementations one or more of the layers contains little or no organicmatter. The same can be said for liquids that may be present in one ormore layers in small amounts. It should also be understood that solidstate material may be deposited or otherwise formed by processesemploying liquid components such as certain processes employing sol-gelsor chemical vapor deposition.

Referring again to FIG. 3B, first an EC layer of WO₃ is deposited, see325. FIGS. 4A-4C are schematic cross-sections depicting formation ofelectrochromic devices in accord with specific methods and apparatus ofthe invention, and specifically in accord with process flow 320.Specifically, FIGS. 4A-4C are used to show three non-limiting examplesof how an EC layer including WO₃ can be formed as part of a stack,wherein an interfacial region serving as an IC layer is formed after theother layers of the stack are deposited. In each of FIGS. 4A-4C, thesubstrate 402, the first TCO layer 404, the CE layer 410 and the secondTCO layer 412 are essentially the same. Also, in each of the threeembodiments, a stack is formed without an IC layer, and then the stackis further processed in order to form an interfacial region that servesas an IC layer within the stack, that is between the EC and the CElayer.

Referring to each of FIGS. 4A-4C, layered structures, 400, 403 and 409,respectively are depicted. Each of these layered structures includes asubstrate, 402, which is, for example, glass. Any material havingsuitable optical, electrical, thermal, and mechanical properties may beused as substrate 402. Such substrates include, for example, glass,plastic, and mirror materials. Suitable plastic substrates include, forexample acrylic, polystyrene, polycarbonate, allyl diglycol carbonate,SAN (styrene acrylonitrile copolymer), poly(4-methyl-1-pentene),polyester, polyamide, etc. and it is preferable that the plastic be ableto withstand high temperature processing conditions. If a plasticsubstrate is used, it is preferably barrier protected and abrasionprotected using a hard coat of, for example, a diamond-like protectioncoating, a silica/silicone anti-abrasion coating, or the like, such asis well known in the plastic glazing art. Suitable glasses includeeither clear or tinted soda lime glass, including soda lime float glass.The glass may be tempered or untempered. In some embodiments,commercially available substrates such as glass substrates contain atransparent conductive layer coating. Examples of such glasses includeconductive layer coated glasses sold under the trademark TEC Glass™ byPilkington of Toledo, Ohio, and SUNGATE™ 300 and SUNGATE™ 500 by PPGIndustries of Pittsburgh, Pa. TEC Glass™ is a glass coated with afluorinated tin oxide conductive layer.

In some embodiments, the optical transmittance (i.e., the ratio oftransmitted radiation or spectrum to incident radiation or spectrum) ofsubstrate 402 is about 90 to 95%, for example, about 90-92%. Thesubstrate may be of any thickness, as long as it has suitable mechanicalproperties to support the electrochromic device. While the substrate 402may be of any size, in some embodiments, it is about 0.01 mm to 10 mmthick, preferably about 3 mm to 9 mm thick.

In some embodiments of the invention, the substrate is architecturalglass. Architectural glass is glass that is used as a building material.Architectural glass is typically used in commercial buildings, but mayalso be used in residential buildings, and typically, though notnecessarily, separates an indoor environment from an outdoorenvironment. In certain embodiments, architectural glass is at least 20inches by 20 inches, and can be much larger, for example, as large asabout 72 inches by 120 inches. Architectural glass is typically at leastabout 2 mm thick. Architectural glass that is less than about 3.2 mmthick cannot be tempered. In some embodiments of the invention witharchitectural glass as the substrate, the substrate may still betempered even after the electrochromic stack has been fabricated on thesubstrate. In some embodiments with architectural glass as thesubstrate, the substrate is a soda lime glass from a tin float line. Thepercent transmission over the visible spectrum of an architectural glasssubstrate (i.e., the integrated transmission across the visiblespectrum) is generally greater than 80% for neutral substrates, but itcould be lower for colored substrates. Preferably, the percenttransmission of the substrate over the visible spectrum is at leastabout 90% (for example, about 90-92%). The visible spectrum is thespectrum that a typical human eye will respond to, generally about 380nm (purple) to about 780 nm (red). In some cases, the glass has asurface roughness of between about 10 nm and about 30 nm. In oneembodiment, substrate 402 is soda glass with a sodium diffusion barrier(not shown) to prevent sodium ions from diffusing into theelectrochromic device. For the purposes of this description, such anarrangement is referred to as “substrate 402.”

Referring again to layered structures, 400, 403 and 409, on top ofsubstrate 402 is deposited a first TCO layer, 404, for example made offluorinated tin oxide or other suitable material, that is, among otherthings, conductive and transparent. Transparent conductive oxidesinclude metal oxides and metal oxides doped with one or more metals.Examples of such metal oxides and doped metal oxides include indiumoxide, indium tin oxide, doped indium oxide, tin oxide, doped tin oxide,zinc oxide, aluminum zinc oxide, doped zinc oxide, ruthenium oxide,doped ruthenium oxide and the like. In one embodiment this second TCOlayer is between about 20 nm and about 1200 nm thick, in anotherembodiment, between about 100 nm and about 600 nm thick, in anotherembodiment about 350 nm thick. The TCO layer should have an appropriatesheet resistance (R_(s)) because of the relatively large area spanned bythe layers. In some embodiments, the sheet resistance of the TCO layersis between about 5 and about 30 Ohms per square. In some embodiments,the sheet resistance of TCO layers is about 15 Ohms per square. Ingeneral, it is desirable that the sheet resistance of each of the twoconductive layers be about the same. In one embodiment, the two layers,for example 404 and 412, each have a sheet resistance of about 10-15Ohms per square.

Each of layered structures 400, 403 and 409, include a stack 414 a, 414b and 414 c, respectively, each of which include the first TCO layer 404on top of substrate 402, a CE layer 410, and a second TCO layer 412. Thedifference in each of layered structures 400, 403 and 409 is how the EClayer was formed, which in turn affects the morphology of the resultantinterfacial region in each scenario.

Consistent with process flow 325 of FIG. 3B, each of stacks 414 a, 414 band 414 c include an electrochromic layer deposited on top of the firstTCO layer 404. The electrochromic layer may contain any one or more of anumber of different electrochromic materials, including metal oxides.Such metal oxides include tungsten oxide (WO₃), molybdenum oxide (MoO₃),niobium oxide (Nb₂O₅), titanium oxide (TiO₂), copper oxide (CuO),iridium oxide (Ir₂O₃), chromium oxide (Cr₂O₃), manganese oxide (Mn₂O₃),vanadium oxide (V₂O₅), nickel oxide (Ni₂O₃), cobalt oxide (CO₂O₃) andthe like. In some embodiments, the metal oxide is doped with one or moredopants such as lithium, sodium, potassium, molybdenum, niobium,vanadium, titanium, and/or other suitable metals or compounds containingmetals. Mixed oxides (for example, W—Mo oxide, W—V oxide) are also usedin certain embodiments, that is, the electrochromic layer includes twoor more of the aforementioned metal oxides. An electrochromic layerincluding a metal oxide is capable of receiving ions transferred from acounter electrode layer.

In some embodiments, tungsten oxide or doped tungsten oxide is used forthe electrochromic layer. In one embodiment of the invention, theelectrochromic layer is made substantially of WO_(x), where “x” refersto an atomic ratio of oxygen to tungsten in the electrochromic layer,and x is between about 2.7 and 3.5. It has been suggested that onlysub-stoichiometric tungsten oxide exhibits electrochromism; i.e.,stoichiometric tungsten oxide, WO₃, does not exhibit electrochromism. Ina more specific embodiment, WO_(x), where x is less than 3.0 and atleast about 2.7 is used for the electrochromic layer. In anotherembodiment, the electrochromic layer is WO_(x), where x is between about2.7 and about 2.9. Techniques such as Rutherford BackscatteringSpectroscopy (RBS) can identify the total number of oxygen atoms whichinclude those bonded to tungsten and those not bonded to tungsten. Insome instances, tungsten oxide layers where x is 3 or greater exhibitelectrochromism, presumably due to unbound excess oxygen along withsub-stoichiometric tungsten oxide. In another embodiment, the tungstenoxide layer has stoichiometric or greater oxygen, where x is 3.0 toabout 3.5. In some embodiments of the invention, at least a portion ofthe EC layer has an excess of oxygen. This more highly oxygenated regionof the EC layer is used as a precursor to formation of an ion conductingelectron insulating region which serves as an IC layer. In otherembodiments a distinct layer of highly oxygenated EC material is formedbetween the EC layer and the CE layer for ultimate conversion, at leastin part, to an ion conducting electrically insulating interfacialregion.

In certain embodiments, the tungsten oxide is crystalline,nanocrystalline, or amorphous. In some embodiments, the tungsten oxideis substantially nanocrystalline, with grain sizes, on average, fromabout 5 nm to 50 nm (or from about 5 nm to 20 nm), as characterized bytransmission electron microscopy (TEM). The tungsten oxide morphology ormicrostructure may also be characterized as nanocrystalline using x-raydiffraction (XRD) and/or electron diffraction, such as selected areaelectron diffraction (SAED). For example, nanocrystalline electrochromictungsten oxide may be characterized by the following XRD features: acrystal size of about 10 to 100 nm, for example, about 55 nm. Further,nanocrystalline tungsten oxide may exhibit limited long range order, forexample, on the order of several (about 5 to 20) tungsten oxide unitcells.

Thus, for convenience, the remainder of process flow 320, in FIG. 3B,will be further described in relation to a first embodiment, includingformation of EC layer 406, represented in FIG. 4A. Then a second andthird embodiment, represented in FIGS. 4B and 4C, respectively, will bedescribed thereafter with particular emphasis on formation andmorphology and/or microstructure of their respective EC layers.

As mentioned with reference to FIG. 3B, an EC layer is deposited, see325. In a first embodiment (represented in FIG. 4A), a substantiallyhomogeneous EC layer, 406, including WO₃ is formed as part of stack 414a, where the EC layer is in direct contact with a CE layer 410. In oneembodiment, the EC layer includes WO₃ as described above. In oneembodiment, heating is applied during deposition of at least a portionof the WO₃. In one particular embodiment, several passes are made past asputter target, where a portion of the WO₃ is deposited on each pass,and heating is applied, for example to substrate 402, after eachdeposition pass to condition the WO₃ prior to deposition of the nextportion of WO₃ of layer 406. In other embodiments, the WO₃ layer may beheated continually during deposition, and deposition can be done in acontinuous manner, rather than several passes with a sputter target. Inone embodiment, the EC layer is between about 300 nm and about 600 nmthick. As mentioned, the thickness of the EC layer depends on upon thedesired outcome and method of forming the IC layer.

In embodiments described in relation to FIG. 4A, the EC layer is WO₃,between about 500 nm and about 600 nm thick, that is sputtered using atungsten target and a sputter gas including between about 40% and about80% O₂ and between about 20% Ar and about 60% Ar, and wherein thesubstrate upon which the WO₃ is deposited is heated, at leastintermittently, to between about 150° C. and about 450° C. duringformation of the EC layer. In a particular embodiment, the EC layer isWO₃, about 550 nm thick, sputtered using the tungsten target, whereinthe sputter gas includes about 50% to about 60% O₂ and about 40% toabout 50% Ar, and the substrate upon which the WO₃ is deposited isheated, at least intermittently, to between about 250° C. and about 350°C. during formation of the electrochromic layer. In these embodiments,the WO₃ layer is substantially homogenous. In one embodiment, the WO₃ issubstantially polycrystalline. It is believed that heating the WO₃, atleast intermittently, during deposition aids in formation of apolycrystalline form of the WO₃.

As mentioned, a number of materials are suitable for the EC layer.Generally, in electrochromic materials, the colorization (or change inany optical property—for example, absorbance, reflectance, andtransmittance) of the electrochromic material is caused by reversibleion insertion into the material (for example, intercalation) and acorresponding injection of a charge balancing electron. Typically somefraction of the ion responsible for the optical transition isirreversibly bound up in the electrochromic material. As describedherein, some or all of the irreversibly bound ions are used tocompensate “blind charge” in the material. In most electrochromicmaterials, suitable ions include lithium ions (Li⁺) and hydrogen ions(H⁺) (i.e., protons). In some cases, however, other ions will besuitable. These include, for example, deuterium ions (D⁺), sodium ions(Na₊), potassium ions (K⁺), calcium ions (Ca⁺⁺), barium ions (Ba⁺⁺),strontium ions (Sr⁺⁺), and magnesium ions (Mg₊₊). In various embodimentsdescribed herein, lithium ions are used to produce the electrochromicphenomena. Intercalation of lithium ions into tungsten oxide (WO_(3−y)(0<y≦˜0.3)) causes the tungsten oxide to change from transparent(bleached state) to blue (colored state). In a typical process where theEC layer includes or is tungsten oxide, lithium is deposited, forexample via sputtering, on EC layer 406 to satisfy the blind charge (aswill be discussed in more detail below with reference to FIGS. 6 and 7),see 330 of the process flow in FIG. 3B. In one embodiment, thelithiation is performed in an integrated deposition system where vacuumis not broken between deposition steps. It should be noted that in someembodiments, lithium is not added at this stage, but rather can be addedafter deposition of the counter electrode layer or in other embodimentslithium is added after the TCO is deposited.

Referring again to FIG. 4A, next a CE layer, 410, is deposited on EClayer 406. In some embodiments, counter electrode layer 410 is inorganicand/or solid. The counter electrode layer may include one or more of anumber of different materials that are capable of serving as reservoirsof ions when the electrochromic device is in the bleached state. Duringan electrochromic transition initiated by, for example, application ofan appropriate electric potential, the counter electrode layer transferssome or all of the ions it holds to the electrochromic layer, changingthe electrochromic layer to the colored state. Concurrently, in the caseof NiO and/or NiWO, the counter electrode layer colors with the loss ofions.

In some embodiments, suitable materials for the counter electrodesinclude nickel oxide (NiO), nickel tungsten oxide (NiWO), nickelvanadium oxide, nickel chromium oxide, nickel aluminum oxide, nickelmanganese oxide, nickel magnesium oxide, chromium oxide (Cr₂O₃),manganese oxide (MnO₂) and Prussian blue. Optically passive counterelectrodes include cerium titanium oxide (CeO₂—TiO₂), cerium zirconiumoxide (CeO₂—ZrO₂), nickel oxide (NiO), nickel-tungsten oxide (NiWO),vanadium oxide (V₂O₅), and mixtures of oxides (for example, a mixture ofNi₂O₃ and WO₃). Doped formulations of these oxides may also be used,with dopants including, for example, tantalum and tungsten. Becausecounter electrode layer 410 contains the ions used to produce theelectrochromic phenomenon in the electrochromic material when theelectrochromic material is in the bleached state, the counter electrodepreferably has high transmittance and a neutral color when it holdssignificant quantities of these ions. The counter electrode morphologymay be crystalline, nanocrystalline, or amorphous.

In some embodiments, where the counter electrode layer isnickel-tungsten oxide, the counter electrode material is amorphous orsubstantially amorphous. Substantially amorphous nickel-tungsten oxidecounter electrodes have been found to perform better, under someconditions, in comparison to their crystalline counterparts. Theamorphous state of the nickel-tungsten oxide may be obtained though theuse of certain processing conditions, described below. While not wishingto be bound to any theory or mechanism, it is believed that amorphousnickel-tungsten oxide is produced by relatively higher energy atoms inthe sputtering process. Higher energy atoms are obtained, for example,in a sputtering process with higher target powers, lower chamberpressures (i.e., higher vacuum), and smaller source to substratedistances. Under the described process conditions, higher density films,with better stability under UV/heat exposure are produced.

In certain embodiments, the amount of nickel present in thenickel-tungsten oxide can be up to about 90% by weight of the nickeltungsten oxide. In a specific embodiment, the mass ratio of nickel totungsten in the nickel tungsten oxide is between about 4:6 and 6:4, inone example, about 1:1. In one embodiment, the NiWO is between about 15%(atomic) Ni and about 60% Ni, and between about 10% W and about 40% W.In another embodiment, the NiWO is between about 30% (atomic) Ni andabout 45% Ni, and between about 15% W and about 35% W. In anotherembodiment, the NiWO is between about 30% (atomic) Ni and about 45% Ni,and between about 20% W and about 30% W. In one embodiment, the NiWO isabout 42% (atomic) Ni and about 14% W.

In one embodiment, CE layer 410 is NiWO as described above, see 335 ofFIG. 3B. In one embodiment, the CE layer is between about 150 nm andabout 300 nm thick, in another embodiment between about 200 nm and about250 nm thick, in another embodiment about 230 nm thick.

In a typical process, lithium is also applied to the CE layer until theCE layer is bleached. It should be understood that reference to atransition between a colored state and bleached state is non-limitingand suggests only one example, among many, of an electrochromictransition that may be implemented. Unless otherwise specified herein,whenever reference is made to a bleached-colored transition, thecorresponding device or process encompasses other optical statetransitions such non-reflective-reflective, transparent-opaque, etc.Further the term “bleached” refers to an optically neutral state, forexample, uncolored, transparent or translucent. Still further, unlessspecified otherwise herein, the “color” of an electrochromic transitionis not limited to any particular wavelength or range of wavelengths. Asunderstood by those of skill in the art, the choice of appropriateelectrochromic and counter electrode materials governs the relevantoptical transition.

In a particular embodiment, lithium, for example via sputtering, isadded to a NiWO CE layer, see 340 of FIG. 3B. In a particularembodiment, an additional amount of lithium is added after sufficientlithium has been introduced to fully bleach the NiWO, see 345 of FIG. 3B(this process is optional, and in one embodiment excess lithium is notadded at this stage in the process). In one embodiment this additionalamount is between about 5% and about 15% excess based on the quantityrequired to bleach the counter electrode layer. In another embodiment,the excess lithium added to the CE layer is about 10% excess based onthe quantity required to bleach the counter electrode layer. After CElayer 410 is deposited, bleached with lithium and additional lithium isadded, a second TCO layer, 412, is deposited on top of the counterelectrode layer, see 350 of FIG. 3B. In one embodiment, the transparentconducting oxide includes indium tin oxide, in another embodiment theTCO layer is indium tin oxide. In one embodiment this second TCO layeris between about 20 nm and about 1200 nm thick, in another embodiment,between about 100 nm and about 600 nm thick, in another embodiment about350 nm thick.

Referring again to FIG. 4A, once layered structure 400 is complete, itis subjected to thermochemical conditioning which converts at least aportion of stack 414 a to an IC layer (if it was not already converteddue to lithium diffusion or other mechanism). Stack 414 a is aprecursor, not an electrochromic device, because it does not yet have anion conducting/electrically insulating layer (or region) between EClayer 406 and CE layer 410. In this particular embodiment, in a two stepprocess, a portion of EC layer 406 is converted to IC layer 408 to makea functional electrochromic device 401. Referring to FIG. 3B, layeredstructure 400 is subjected to an MTCC, see 355. In one embodiment, thestack is first subjected to heating, under inert atmosphere (for exampleargon) at between about 150° C. and about 450° C., for between about 10minutes and about 30 minutes, and then for between about 1 minutes andabout 15 minutes under O₂. In another embodiment, the stack is heated atabout 250° C., for about 15 minutes under inert atmosphere, and thenabout 5 minutes under O₂. Next, layered structure 400 is subjected toheating in air. In one embodiment the stack is heated in air at betweenabout 250° C. and about 350° C., for between about 20 minutes and about40 minutes; in another embodiment the stack is heated in air at about300° C. for about 30 minutes. The energy required to implement MTCC neednot be radiant heat energy. For example, in one embodiment ultravioletradiation is used to implement MTCC. Other sources of energy could alsobe used without escaping the scope of the invention.

After the multistep thermochemical conditioning, process flow 320 iscomplete and a functional electrochromic device is created. Asmentioned, and while not wishing to be bound by theory, it is believedthat the lithium in stack 414 a along with a portion of EC layer 406and/or CE layer 410 combine to form interfacial region 408 whichfunctions as an IC layer. Interfacial region 408 is believed to beprimarily lithium tungstate, Li₂WO₄, which is known to have good ionconducting and electrically insulating properties relative totraditional IC layer materials. As discussed above, precisely how thisphenomenon occurs is not yet known. There are chemical reactions thatmust take place during the multistep thermochemical conditioning to formthe ion conducting electrically insulating region 408 between the EC andCE layers, but also it is thought that an initial flux of lithiumtraveling through the stack, for example provided by the excess lithiumadded to the CE layer as described above, plays a part in formation ofIC layer 408. The thickness of the ion conducting electronicallyinsulating region may vary depending on the materials employed andprocess conditions for forming the layer. In some embodiments,interfacial region 408 is about 10 nm to about 150 nm thick, in anotherembodiment about 20 nm to about 100 nm thick, and in other embodimentsbetween about 30 nm to about 50 nm thick.

As mentioned above, there are a number of suitable materials for makingthe EC layer. As such, using, for example lithium or other suitableions, in the methods described above one can make other interfacialregions that function as IC layers starting from oxygen rich ECmaterials. Suitable EC materials for this purpose include, but are notlimited to SiO₂, Nb₂O₅, Ta₂O₅, TiO₂, ZrO₂ and CeO₂. In particularembodiments where lithium ions are used, ion conducting materials suchas but not limited to, lithium silicate, lithium aluminum silicate,lithium aluminum borate, lithium aluminum fluoride, lithium borate,lithium nitride, lithium zirconium silicate, lithium niobate, lithiumborosilicate, lithium phosphosilicate, and other such lithium-basedceramic materials, silicas, or silicon oxides, including lithiumsilicon-oxide can be made as interfacial regions that function as IClayers.

As mentioned, in one embodiment, the precursor of the ion conductingregion is an oxygen-rich (super-stoichiometric) layer that istransformed into ion-conducting/electron-insulating region vialithiation and MTCC as described herein. While not wishing to be boundto theory, it is believed that upon lithiation, the excess oxygen formslithium oxide, which further forms lithium salts, that is, lithiumelectrolytes, such as lithium tungstate (Li₂WO₄), lithium molybdate(Li₂MoO₄), lithium niobate (LiNbO₃), lithium tantalate (LiTaO₃), lithiumtitanate (Li₂TiO₃), lithium zirconate (Li₂ZrO₃) and the like. In oneembodiment, the interfacial region comprises at least one of tungstenoxide (WO_(3+x), 0≦x≦1.5), molybdenum oxide (MoO_(3+x), 0≦x≦1.5),niobium oxide (Nb₂O_(5+x), 0≦x≦2), titanium oxide (TiO_(2+x), 0≦x≦1.5),tantalum oxide (Ta₂O_(5+x), 0≦x≦2), zirconium oxide (ZrO_(2+x), 0≦x≦1.5)and cerium oxide (CeO_(2+x), 0≦x≦1.5).

Any material, however, may be used for the ion conducting interfacialregion provided it can be fabricated with low defectivity and it allowsfor the passage of ions between the counter electrode layer 410 to theelectrochromic layer 406 while substantially preventing the passage ofelectrons. The material may be characterized as being substantiallyconductive to ions and substantially resistive to electrons. In oneembodiment, the ion conductor material has an ionic conductivity ofbetween about 10⁻¹⁰ Siemens/cm (or ohm⁻¹ cm⁻¹) and about 10⁻³ Siemens/cmand an electronic resistivity of greater than 10⁵ ohms-cm. In anotherembodiment, the ion conductor material has an ionic conductivity ofbetween about 10⁻⁸ Siemens/cm and about 10⁻³ Siemens/cm and anelectronic resistivity of greater than 10¹⁰ ohms-cm. While ionconducting layers should generally resist leakage current (for example,providing a leakage current of not more than about 15 μA/cm², it hasbeen found that some devices fabricated as described herein havesurprising high leakage currents, for example, between about 40 μA/cmand about 150 μA/cm, yet provide good color change across the device andoperate efficiently.

As mentioned above, there are at least two other ways of creating an ionconducting electrically insulating region between the EC and CE layers,after formation of the stack. These additional embodiments are describedbelow with reference to a particular example where tungsten oxide isused for the EC layer. Also, as mentioned above, the interfacial regionwith IC properties may form in situ during fabrication of the stackwhen, for example, lithium diffusion or heat converts some of the ECand/or CE layer to the interfacial region.

In general, there are certain benefits to creating the ion conductingregion later in the process. First, the ion conducting material may beprotected from some of the harsh processing that occurs duringdeposition and lithiation of the EC and CE layers. For example, thedeposition of these layers by a plasma process is often accompanied by alarge voltage drop proximate the stack, frequently in the neighborhoodof 15-20 volts. Such large voltages can damage or cause break down ofthe sensitive ion conducting material. By shifting the IC materialformation to later in the process, the material is not exposed topotentially damaging voltage extremes. Second, by forming the ICmaterial later in the process, one may have better control over someprocess conditions that are not possible prior to completion of both theEC and CE layers. These conditions include lithium diffusion and currentflow between electrodes. Controlling these and other conditions late inthe process provides additional flexibility to tailor the physical andchemical properties of the IC material to particular applications. Thus,not all of the benefits of the invention are due to the uniqueinterfacial region acting as an IC layer, that is, there aremanufacturing and other benefits as well.

It has been observed that ion conducting materials formed in accordancewith some of the embodiments described herein have superior performancewhen compared to devices fabricated using conventional techniques forforming an IC layer (for example, PVD from an IC material target). Thedevice switching speed, for example, has been found to be very fast, forexample less than 10 minutes, in one example about eight minutes, toachieve about 80% of end state compared to 20-25 minutes or more fortraditional devices. In some instances, devices described herein haveswitching speeds orders of magnitude better than conventional devices.This is possibly attributable to the greater amounts of readilytransferable lithium disposed in the interfacial region and/or thegraded interfaces, for example between the EC and interfacial regionand/or between the CE and the interfacial region. Such lithium may be inthe EC and/or CE phases intermixed with the IC phase present in theinterfacial region. It is also due possibly to the relatively thin layeror network of IC material present in the interfacial region. In supportof this view, it has been observed that some devices fabricated inaccordance with the teachings herein have high leakage currents, yetsurprisingly exhibit good color change and good efficiency. In somecases, the leakage current density of solidly performing devices hasbeen found to be at least about 100 μA/cm.

Referring now to FIG. 4B, in a second embodiment, the initially laiddown EC material of stack 414 b is really two layers: a first WO₃ layer,406, analogous to layer 406 in FIG. 4A, but between about 350 nm andabout 450 nm thick, that is sputtered using a tungsten target and afirst sputter gas including between about 40% and about 80% O₂ andbetween about 20% Ar and about 60% Ar, and a second WO₃ layer, 405,between about 100 nm and about 200 nm thick, that is sputtered using thetungsten target and a second sputter gas including between about 70% and100% O₂ and between 0% Ar and about 30% Ar. In this embodiment, heat isapplied, for example by heating substrate 402, at least intermittently,to between about 150° C. and about 450° C. during deposition of thefirst WO₃ layer, 406, but not, or substantially not, heated duringdeposition of the second WO₃ layer 405. In a more specific embodiment,layer 406 is about 400 nm thick and the first sputter gas includesbetween about 50% and about 60% O₂ and between about 40% and about 50%Ar; the second WO₃ layer 405 is about 150 nm thick and the secondsputter gas is substantially pure O₂. In this embodiment, heat isapplied, at least intermittently, to between about 200° C. and about350° C. during formation of the first WO₃ layer, 406, but not, orsubstantially not, heated during formation of the second WO₃ layer 405.In this way, the first WO₃ layer is substantially polycrystalline, whilethe second WO₃ layer is not necessarily so.

Referring again to FIG. 4B, as described above in relation to FIGS. 3Band 4A, the stack is completed by lithiation of EC layer(s) 406 and 405to approximately or substantially satisfy the blind charge, depositionof CE layer 410, lithiation of the CE layer to bleach state, addition ofadditional lithium, and deposition of the second TCO layer 412 tocomplete layered stack 403. Analogous thermochemical conditioning isperformed on layered stack 403 to provide layered stack 407, afunctional electrochromic device including an ion conductingelectrically insulating region 408 a. While not wishing to be bound bytheory, in this example, it is believed that the oxygen rich layer 405of WO₃ serves primarily as the source of precursor material to forminterfacial region 408 a. In this example, the entire oxygen rich WO₃layer is depicted as converting to interfacial region 408 a, however ithas been found that this is not always the case. In some embodiments,only a portion of an oxygen rich layer is converted to form aninterfacial region that serves the function of an IC layer.

Referring now to FIG. 4C, in a third embodiment, layered stack 409includes an EC layer, 406 a, which has a graded composition of WO₃ andis formed as part of a stack, 414 c, where the graded compositionincludes varying levels of oxygen. In one non-limiting example, there isa higher concentration of oxygen in EC layer 406 a at the EC-CE layer(410) interface than, for example, at the interface of TCO layer 404with EC layer 406 a.

In one embodiment, EC layer 406 a is a graded composition WO₃ layer,between about 500 nm and about 600 nm thick, that is sputtered using atungsten target and a sputter gas, wherein the sputter gas includesbetween about 40% and about 80% O₂ and between about 20% Ar and about60% Ar at the start of sputtering the electrochromic layer, and thesputter gas includes between about 70% and 100% O₂ and between 0% Ar andabout 30% Ar at the end of sputtering the electrochromic layer, andwherein heat is applied, for example to substrate 402, at leastintermittently, to between about 150° C. and about 450° C. at thebeginning of formation of EC layer 406 a but not, or substantially not,applied during deposition of at least a final portion of EC layer 406 a.In a more specific embodiment, the graded composition WO₃ layer is about550 nm thick; the sputter gas includes between about 50% and about 60%O₂ and between about 40% and about 50% Ar at the start of sputtering theelectrochromic layer, and the sputter gas is substantially pure O₂ atthe end of sputtering the electrochromic layer; and wherein heat isapplied, for example to substrate 402, at least intermittently, tobetween about 200° C. and about 350° C. at the beginning of formation ofthe electrochromic layer but not, or substantially not, applied duringdeposition of at least a final portion of the electrochromic layer. Inone embodiment heat is applied at the described temperature ranges atthe onset of deposition and gradually decreased to no applied heat at apoint where about half of the EC layer is deposited, while the sputtergas composition is adjusted from between about 50% and about 60% O₂ andbetween about 40% and about 50% Ar to substantially pure O₂ along asubstantially linear rate during deposition of the EC layer.

More generally, the interfacial region typically, though notnecessarily, has a heterogeneous structure that includes at least twodiscrete components represented by different phases and/or compositions.Further, the interfacial region may include a gradient in these two ormore discrete components such as an ion conducting material and anelectrochromic material (for example, a mixture of lithium tungstate andtungsten oxide). The gradient may provide, for example, a variablecomposition, microstructure, resistivity, dopant concentration (forexample, oxygen concentration), stoichiometry, density, and/or grainsize regime. The gradient may have many different forms of transitionincluding a linear transition, a sigmoidal transition, a Gaussiantransition, etc. In one example, an electrochromic layer includes atungsten oxide region that transitions into a superstoichiometrictungsten oxide region. Part or all of the superstoichiometric oxideregion is converted to the interfacial region. In the final structure,the tungsten oxide region is substantially polycrystalline and themicrostructure transitions to substantially amorphous at the interfacialregion. In another example, an electrochromic layer includes a tungstenoxide region that transitions into a niobium (superstoichiometric) oxideregion. Part or all of the niobium oxide region is converted to theinterfacial region. In the final structure, the tungsten oxide region issubstantially polycrystalline and the microstructure transitions tosubstantially amorphous at the interfacial region.

Referring again to FIG. 4C, as described above in relation to FIGS. 3Band 4A, the stack is completed by lithiation of EC layer 406 a toapproximately or substantially satisfy the blind charge, deposition ofCE layer 410, lithiation of the CE layer to bleach state, addition ofadditional lithium, and deposition of the second TCO layer 412 tocomplete layered stack 409. Analogous multistep thermochemicalconditioning is performed on layered stack 409 to provide layered stack411, a functional electrochromic device including an ion conductingelectrically insulating region 408 b and at least a portion of originalgraded EC layer 406 a which serves as the EC layer in the functionalelectrochromic device 411. While not wishing to be bound by theory, inthis example, it is believed that uppermost oxygen rich portion of thegraded layer of WO₃ primarily forms graded interfacial region 408 b.While not wishing to be bound by theory, there is the possibility thatformation of the interfacial region is self-limiting and depends onrelative amounts of oxygen, lithium, electrochromic material and/orcounter electrode material in the stack.

In various embodiments described herein, the electrochromic stack isdescribed as not, or substantially not, being heated during certainprocessing phases. In one embodiment, the stack is cooled, actively orpassively (for example using a heat sink), after a heating step.Apparatus of the invention include active and passive coolingcomponents, for example, active cooling can include platens that arecooled via fluid circulation, cooling via exposure to cooled (e.g. viaexpansion) gases, refrigeration units and the like. Passive coolingcomponents can include heat sinks, such as blocks of metal and the like,or simply removing the substrate from exposure to heat.

Another aspect of the invention is a method of fabricating anelectrochromic device, the method including: (a) forming either anelectrochromic layer including an electrochromic material or a counterelectrode layer including a counter electrode material; (b) forming anintermediate layer over the electrochromic layer or the counterelectrode layer, where the intermediate layer includes an oxygen richform of at least one of the electrochromic material, the counterelectrode material and an additional material, where the additionalmaterial includes distinct electrochromic or counter electrode material,where the intermediate layer is not substantially electronicallyinsulating; (c) forming the other of the electrochromic layer and thecounter electrode layer; and (d) allowing at least a portion of theintermediate layer to become substantially electronically insulating. Inone embodiment, the electrochromic material is WO₃. In anotherembodiment, (a) includes sputtering WO₃ using a tungsten target and afirst sputter gas including between about 40% and about 80% O₂ andbetween about 20% Ar and about 60% Ar, to reach of thickness of betweenabout 350 nm and about 450 nm, and heating, at least intermittently, tobetween about 150° C. and about 450° C. during formation of theelectrochromic layer. In another embodiment, (b) includes sputtering WO₃using a tungsten target and a second sputter gas including between about70% and 100% O₂ and between 0% Ar and about 30% Ar, to reach a thicknessof between about 100 nm and about 200 nm, without heating. In yetanother embodiment, the method further includes sputtering lithium ontothe intermediate layer until the blind charge is approximately orsubstantially satisfied. In one embodiment, the counter electrode layerincludes NiWO, between about 150 nm and about 300 nm thick. In anotherembodiment, lithium is sputtered onto counter electrode layer until thecounter electrode layer is bleached. In another embodiment, anadditional amount of lithium, between about 5% and about 15% excessbased on the quantity required to bleach the counter electrode layer, issputtered onto the counter electrode layer. In another embodiment, atransparent conducting oxide layer is deposited on top of the counterelectrode layer. In one embodiment the transparent conducting oxideincludes indium tin oxide, in another embodiment, the transparentconducting oxide is indium tin oxide. In another embodiment, the stackformed from the above embodiments is heated at between about 150° C. andabout 450° C., for between about 10 minutes and about 30 minutes underAr, and then for between about 1 minutes and about 15 minutes under O₂,and then heated in air at between about 250° C. and about 350° C., forbetween about 20 minutes and about 40 minutes.

In another embodiment, (a) includes sputtering a first electrochromicmaterial of formula MO_(x), wherein M is a metal or metalloid elementand x indicates stoichiometric oxygen to M ratio, and (b) includessputtering a second electrochromic material of formula NO_(y) as theintermediate layer, where N is the same or a different metal ormetalloid element and y indicates a superstoichiometric amount of oxygento N ratio. In one embodiment, M is tungsten and N is tungsten. Inanother embodiment, M is tungsten and N is selected from the groupconsisting of niobium, silicon, tantalum, titanium, zirconium andcerium.

Another embodiment of the invention is an electrochromic deviceincluding: (a) an electrochromic layer including an electrochromicmaterial; (b) a counter electrode layer including a counter electrodematerial; and (c) an interfacial region between the electrochromic layerand the counter electrode layer, wherein the interfacial region includesan electronically insulating ion conducting material and at least one ofthe electrochromic material, the counter electrode material and anadditional material, where the additional material includes distinctelectrochromic or counter electrode material.

In one embodiment, the electronically insulating ion conducting materialand at least one of the electrochromic material, the counter electrodematerial and the additional material are substantially evenlydistributed within the interfacial region. In another embodiment, theelectronically insulating ion conducting material and at least one ofthe electrochromic material, the counter electrode material and theadditional material include a composition gradient in a directionperpendicular to the layers. In another embodiment, consistent witheither of the two aforementioned embodiments, the electronicallyinsulating ion conducting material includes lithium tungstate, theelectrochromic material includes a tungsten oxide and the counterelectrode material includes nickel tungsten oxide. In a specificimplementation of the aforementioned embodiment, there is no additionalmaterial. In one embodiment, the electrochromic layer is between about300 nm and about 500 nm thick, the interfacial region is between about10 nm and about 150 nm thick, and the counter electrode layer is betweenabout 150 nm and about 300 nm thick. In another embodiment, theelectrochromic layer is between about 400 nm and about 500 nm thick; theinterfacial region is between about 20 nm and about 100 nm thick, andthe counter electrode layer is between about 150 and about 250 nm thick.In yet another embodiment, the electrochromic layer is between about 400nm and about 450 nm thick; the interfacial region is between about 30 nmand about 50 nm thick, and the counter electrode layer is about 200 nmand about 250 nm thick.

Another embodiment is a method of fabricating an electrochromic device,the method including:

-   -   depositing an electrochromic layer by sputtering a tungsten        target with a sputter gas comprising between about 40% and about        80% O₂ and between about 20% Ar and about 60% Ar to produce WO₃        to a thickness of between about 500 nm and about 600 nm, wherein        the substrate upon which the WO₃ is deposited is heated, at        least intermittently, to between about 150° C. and about 450° C.        during formation of the electrochromic layer;    -   sputtering lithium onto the electrochromic layer until the blind        charge is satisfied;    -   depositing a counter electrode layer on the electrochromic layer        without first providing an ion conducting electronically        insulating layer between the electrochromic layer and the        counter electrode layer, wherein the counter electrode layer        includes NiWO;    -   sputtering lithium onto the counter electrode layer until the        counter electrode layer is substantially bleached; and

forming an interfacial region between the electrochromic layer and thecounter electrode layer, wherein said interfacial region issubstantially ion conducting and substantially electronicallyinsulating. In one embodiment, forming the interfacial region includesMTCC of the stack, alone or along with substrate, conductive and/orencapsulation layers.

The electrochromic devices of the invention can include one or moreadditional layers (not shown) such as one or more passive layers, forexample to improve certain optical properties, providing moisture orscratch resistance, to hermetically seal the electrochromic device andthe like. Typically, but not necessarily, a capping layer is depositedon the electrochromic stack. In some embodiments, the capping layer isSiAlO. In some embodiments, the capping layer is deposited bysputtering. In one embodiment, the thickness of a capping layer isbetween about 30 nm and about 100 nm.

From the discussion above, it should be appreciated that electrochromicdevices of the invention can be made in a single chamber apparatus, forexample a sputter tool, that has, for example, a tungsten target, anickel target and a lithium target along with oxygen and argon sputtergases. As mentioned, due to the nature of the interfacial regions formedto serve the purpose of a conventional distinct IC layer, a separatetarget for sputtering an IC layer is not necessary. Of particularinterest to the inventors is fabricating electrochromic devices of theinvention, for example, in a high throughput fashion, therefore it isdesirable to have apparatus that can fabricate electrochromic devices ofthe invention sequentially as substrates pass through an integrateddeposition system. For example, the inventors are particularlyinterested in fabricating electrochromic devices on windows,particularly architectural glass scale windows (supra).

Thus, another aspect of the invention is an apparatus for fabricating anelectrochromic device, including: an integrated deposition systemincluding: (i) a first deposition station containing a material sourceconfigured to deposit an electrochromic layer including anelectrochromic material; and (ii) a second deposition station configuredto deposit a counter electrode layer including a counter electrodematerial; and a controller containing program instructions for passingthe substrate through the first and second deposition stations in amanner that sequentially deposits a stack on the substrate, the stackhaving an intermediate layer sandwiched in between the electrochromiclayer and the counter electrode layer; wherein either or both of thefirst deposition station and the second deposition station are alsoconfigured to deposit the intermediate layer over the electrochromiclayer or the counter electrode layer, and where the intermediate layerincludes an oxygen rich form of the electrochromic material or thecounter electrode material and where the first and second depositionstations are interconnected in series and operable to pass a substratefrom one station to the next without exposing the substrate to anexternal environment. In one embodiment, apparatus of the invention areoperable to pass the substrate from one station to the next withoutbreaking vacuum and may include one or more lithiation stations operableto deposit lithium from a lithium-containing material source on one ormore layers of the electrochromic device. In one embodiment, apparatusof the invention are operable to deposit the electrochromic stack on anarchitectural glass substrate.

In one embodiment, the apparatus is operable to pass the substrate fromone station to the next without breaking vacuum. In another embodiment,the integrated deposition system further includes one or more lithiationstations operable to deposit lithium from a lithium-containing materialsource on at least one of the electrochromic layer, the intermediatelayer and the counter electrode layer. In yet another embodiment, theintegrated deposition system is operable to deposit the stack on anarchitectural glass substrate. In another embodiment, the integrateddeposition system further includes a substrate holder and transportmechanism operable to hold the architectural glass substrate in avertical orientation while passing through the integrated depositionsystem. In another embodiment, the apparatus further includes one ormore load locks for passing the substrate between an externalenvironment and the integrated deposition system. In another embodiment,the apparatus further includes at least one slit valve operable topermit isolation of said one or more lithium deposition stations from atleast one of the first deposition station and the second depositionstation. In one embodiment, the integrated deposition system includesone or more heaters configured to heat the substrate.

FIG. 5 depicts a simplified representation of an integrated depositionsystem 500 in a perspective view and with more detail including acutaway view of the interior. In this example, system 500 is modular,where entry load lock 502 and exit load lock 504 are connected todeposition module 506. There is an entry port, 510, for loading, forexample, architectural glass substrate 525 (load lock 504 has acorresponding exit port). Substrate 525 is supported by a pallet, 520,which travels along a track, 515. In this example, pallet 520 issupported by track 515 via hanging but pallet 520 could also besupported atop a track located near the bottom of apparatus 500 or atrack, for example mid-way between top and bottom of apparatus 500.Pallet 520 can translate (as indicated by the double headed arrow)forward and/or backward through system 500. For example during lithiumdeposition, the substrate may be moved forward and backward in front ofa lithium target, 530, making multiple passes in order to achieve adesired lithiation. This function is not limited to lithium targets,however, for example a tungsten target may pass multiple times past asubstrate, or the substrate may pass by via forward/backward motion pathin front of the tungsten target to deposit, for example, anelectrochromic layer. Pallet 520 and substrate 525 are in asubstantially vertical orientation. A substantially vertical orientationis not limiting, but it may help to prevent defects because particulatematter that may be generated, for example, from agglomeration of atomsfrom sputtering, will tend to succumb to gravity and therefore notdeposit on substrate 525. Also, because architectural glass substratestend to be large, a vertical orientation of the substrate as ittraverses the stations of the integrated deposition system enablescoating of thinner glass substrates since there are less concerns oversag that occurs with thicker hot glass.

Target 530, in this case a cylindrical target, is oriented substantiallyparallel to and in front of the substrate surface where deposition is totake place (for convenience, other sputter means are not depicted here).Substrate 525 can translate past target 530 during deposition and/ortarget 530 can move in front of substrate 525. The movement path oftarget 530 is not limited to translation along the path of substrate525. Target 530 may rotate along an axis through its length, translatealong the path of the substrate (forward and/or backward), translatealong a path perpendicular to the path of the substrate, move in acircular path in a plane parallel to substrate 525, etc. Target 530 neednot be cylindrical, it can be planar or any shape necessary fordeposition of the desired layer with the desired properties. Also, theremay be more than one target in each deposition station and/or targetsmay move from station to station depending on the desired process. Thevarious stations of an integrated deposition system of the invention maybe modular, but once connected, form a continuous system where acontrolled ambient environment is established and maintained in order toprocess substrates at the various stations within the system.

More detailed aspects of how electrochromic materials are depositedusing integrated deposition system 500 are described in U.S.Non-Provisional patent application Ser. Nos. 12/645,111 and 12/645,159,supra.

Integrated deposition system 500 also has various vacuum pumps, gasinlets, pressure sensors and the like that establish and maintain acontrolled ambient environment within the system. These components arenot shown, but rather would be appreciated by one of ordinary skill inthe art. System 500 is controlled, for example, via a computer system orother controller, represented in FIG. 5 by an LCD and keyboard, 535. Oneof ordinary skill in the art would appreciate that embodiments of thepresent invention may employ various processes involving data stored inor transferred through one or more computer systems. Embodiments of thepresent invention also relate to the apparatus, such computers andmicrocontrollers, for performing these operations. These apparatus andprocesses may be employed to deposit electrochromic materials of methodsof the invention and apparatus designed to implement them. The controlapparatus of this invention may be specially constructed for therequired purposes, or it may be a general-purpose computer selectivelyactivated or reconfigured by a computer program and/or data structurestored in the computer. The processes presented herein are notinherently related to any particular computer or other apparatus. Inparticular, various general-purpose machines may be used with programswritten in accordance with the teachings herein, or it may be moreconvenient to construct a more specialized apparatus to perform and/orcontrol the required method and processes.

From the description above, particularly of FIGS. 3A-3B, it can be seenthat with methods of the invention, one can not only make electrochromicdevices, but also prefabricate a layered stack, for example 400, 403 and409, that can in some cases be converted through subsequent processing,for example as described herein, to an electrochromic device. Though notfunctional electrochromic devices, by virtue of not having an ionconducting and electrically insulating region between the EC and CElayers, such “electrochromic device precursors” can be of particularvalue. This is especially true if the device precursors are manufacturedin a high purity, integrated processing apparatus as described herein,where the material layers are all deposited under a controlled ambientenvironment where, for example, vacuum is never broken.

In that way, high purity, low-defect materials are stacked andessentially “sealed,” for example, by the final TCO layer and/or acapping layer prior to leaving the integrated system.

Like the electrochromic devices of the invention described above,electrochromic device precursors can also include one or more additionallayers (not shown) such as one or more passive layers, for example toimprove certain optical properties, providing moisture or scratchresistance, to hermetically seal the device precursor and the like. Inone embodiment, a capping layer is deposited on the TCO layer of theprecursor stack. In some embodiments, the capping layer is SiAlO. Insome embodiments, the capping layer is deposited by sputtering. In oneembodiment, the thickness of a capping layer is between about 30 nm andabout 100 nm. Subsequent processing with the cap layer in place formsthe IC layer without contamination from the environment, that is, withthe additional protection of the capping layer.

Conversion to the functional electrochromic device can occur outside theintegrated system if desired, since the internal stack structure isprotected from the outside environment and somewhat less stringentpurity conditions are necessary for the last conditioning steps toconvert the precursor stack to the functional device. Such stackedelectrochromic device precursors can have advantages, for example,longer lifespan due to conversion to the electrochromic device only whenneeded, flexibility by having, for example, a single precursor stackthat can be stored and used when conversion parameters are improved orfed to different conversion chambers and/or customer sites forconversion depending on the needs of the final product and qualitystandards that must be met. Also such precursor stacks are useful fortesting purposes, for example, quality control or research efforts.

Accordingly, one embodiment of the invention is an electrochromic deviceprecursor including: (a) a substrate; (b) a first transparent conductingoxide layer on the substrate; (c) a stack on the first transparentconducting oxide layer, the stack including: (i) an electrochromic layerincluding an electrochromic material, and (ii) a counter electrode layerincluding a counter electrode material; where the stack does not includean ion conducting and electrically insulating region between theelectrochromic layer and the counter electrode layer; and (d) a secondtransparent conducting oxide layer on top of the stack. In oneembodiment, the electrochromic layer includes tungsten oxide and thecounter electrode layer comprises nickel tungsten oxide. In oneembodiment, at least one of the stack and the electrochromic layercontain lithium. In another embodiment, the electrochromic layer istungsten oxide with a superstoichiometric oxygen content at least at theinterface with the counter electrode layer. In another embodiment, thestack includes an IC precursor layer between the counter electrode layerand the electrochromic layer, the IC precursor layer including tungstenoxide with a higher oxygen content than that of the electrochromiclayer. In one embodiment, where there is no IC precursor layer betweenthe EC and CE layers, the electrochromic layer is between about 500 nmand about 600 nm thick and the counter electrode layer is between about150 nm and about 300 nm thick. In another embodiment, where there is anIC precursor layer between the EC and CE layers, the electrochromiclayer is between about 350 nm and about 400 nm thick, the IC precursorlayer is between about 20 nm and about 100 nm thick, and the counterelectrode layer is between about 150 nm and about 300 nm thick. In oneembodiment, precursor devices described herein are exposed to heating toconvert them to functional electrochromic devices. In one embodiment,the heating is part of an MTCC.

Another embodiment is an electrochromic device including: (a) anelectrochromic layer including an electrochromic material, and (b) acounter electrode layer including a counter electrode material, whereinthe device does not contain a compositionally homogeneous layer ofelectrically insulating, ion conducting material between theelectrochromic layer and the counter electrode layer. In one embodiment,the electrochromic material is tungsten oxide, the counter electrodematerial is nickel tungsten oxide, and between the electrochromic layerand the counter electrode layer is an interfacial region including amixture of lithium tungstate and at least one of tungsten oxide andnickel tungsten oxide. In another embodiment, the electrochromic layeris between about 300 nm and about 500 nm thick; the interfacial regionis between about 10 nm and about 150 nm thick, and the counter electrodelayer is between about 150 nm and about 300 nm thick.

EXAMPLES

FIG. 6, is a graph of a process flow used as a protocol for fabricatingelectrochromic devices of the invention. They axis units are opticaldensity and the x axis units are time/process flow. In this example, anelectrochromic device is fabricated analogous to that described inrelation to FIG. 4A, where the substrate is glass with fluorinated tinoxide as the first TCO, the EC layer is WO₃ with excess oxygen in thematrix (for example, sputtered using the tungsten target, where thesputter gas is about 60% O₂ and about 40% Ar), the CE layer is formedatop the EC layer and is made of NiWO and the second TCO is indium tinoxide (ITO). Lithium is used as the ion source for the electrochromictransition.

Optical density is used to determine endpoints during fabrication of theelectrochromic device. Starting at the origin of the graph, opticaldensity is measured as the EC layer, WO₃, is deposited on the substrate(glass+TCO). The optical density of the glass substrate has a baselinevalue optical density of about 0.07 (absorbance units). The opticaldensity increases from that point as the EC layer builds, becausetungsten oxide, although substantially transparent, absorbs some visiblelight. For a desired thickness of the tungsten oxide layer about 550 nmthick, as described above, the optical density rises to about 0.2. Afterdeposition of the tungsten oxide EC layer, lithium is sputtered on theEC layer as indicated by the first time period denoted “Li.” During thisperiod, the optical density increases along a curve further to about0.4, indicating that the blind charge of the tungsten oxide has beensatisfied, as tungsten oxide colors as lithium is added. The time perioddenoted “NiWO” indicates deposition of the NiWO layer, during which theoptical density increases because NiWO is colored. The optical densityincreases further during NiWO deposition from about 0.4 to about 0.9 forthe addition of a NiWO layer about 230 nm thick. Note that some lithiummay diffuse from the EC layer to the CE layer as the NiWO is deposited.This serves to maintain the optical density at a relatively lower valueduring the NiWO deposition, or at least during the initial phase of thedeposition.

The second time period denoted “Li” indicates addition of lithium to theNiWO EC layer. The optical density decreases from about 0.9 to about 0.4during this phase because lithiation of the NiWO bleaches the NiWO.Lithiation is carried out until the NiWO is bleached, including a localminima at about 0.4 optical density. The optical density bottoms out atabout 0.4 because the WO₃ layer is still lithiated and accounts for theoptical density. Next, as indicated by time period “extra Li” additionallithium is sputtered onto the NiWO layer, in this example about 10%additional lithium as compared to that added to the NiWO to bleach it.During this phase the optical density increases slightly. Next theindium tin oxide TCO is added, as indicated by “ITO” in the graph.Again, the optical density continues to rise slightly during formationof the indium tin oxide layer, to about 0.6. Next, as indicated by timeperiod denoted “MSTCC” the device is heated to about 250° C., for about15 minutes under Ar, and then about 5 minutes under O₂. Then the deviceis annealed in air at about 300° C. for about 30 minutes. During thistime, the optical density decreases to about 0.4. Thus optical densityis a useful tool for fabricating devices of the invention, for examplefor determining layer thickness based on material deposited andmorphology, and especially for titrating lithium onto the various layersfor satisfying blind charge and/or reaching a bleached state.

FIG. 7 shows a cross section TEM of an electrochromic device 700fabricated using methods of the invention, consistent with the protocolas described in relation to FIG. 6. Device 700 has a glass substrate 702upon which an electrochromic stack, 714, is formed. Substrate 702 has anITO layer, 704, which serves as the first TCO. A tungsten oxide EClayer, 706, is deposited on TCO 704. Layer 706 was formed at a thicknessof about 550 nm, that is, WO₃ formed via sputtering tungsten with oxygenand argon as described above in relation to FIG. 6. To the EC layer wasadded lithium. Then a CE layer, 710, of NiWO, about 230 nm thick, wasadded followed by addition of lithium to bleach and then about 10%excess. Finally an indium tin oxide layer, 712, was deposited and thestack was subjected to multistep thermochemical conditioning asdescribed above in relation to FIG. 4A. After the MSTCC, this TEM wastaken. As seen, a new region, 708, which is ion conductingelectronically insulating, was formed.

FIG. 7 also shows five selected area electron diffraction (SAED)patterns for the various layers. First, 704 a, indicates that the ITOlayer is highly crystalline. Pattern 706 a shows that the EC layer ispolycrystalline. Pattern 708 a shows that the IC layer is substantiallyamorphous. Pattern 710 a shows that the CE layer is polycrystalline.Finally, pattern 712 a shows that the indium tin oxide TCO layer ishighly crystalline.

FIG. 8 is a cross section of a device, 800, of the invention analyzed byscanning transmission electron microscopy (STEM). In this example,device 800 was fabricated using methods of the invention, consistentwith the protocol as described in relation to FIG. 4B. Device 800 is anelectrochromic stack formed on a glass substrate (not labeled). On theglass substrate is a fluorinated tin oxide layer, 804, which serves asthe first TCO (sometimes called a “TEC” layer, for transparentelectronic conductor”). A tungsten oxide EC layer, 806, was deposited onTCO 804. In this example, layer 806 was formed at a thickness of about400 nm, that is, WO₃ formed via sputtering tungsten with oxygen andargon as described above in relation to FIG. 6, then an oxygen richprecursor layer, 805, was deposited to a thickness of about 150 nm. Tolayer 805 was added lithium. Then a CE layer, 810, of NiWO, about 230 nmthick, was added followed by addition of lithium to bleach and thenabout 10% excess. Finally an indium tin oxide layer, 812, was depositedand the stack was subjected to multistep thermochemical conditioning asdescribed above in relation to FIG. 4B. After the MSTCC, this STEM wastaken. As seen, a new region, 808, which is ion conductingelectronically insulating, was formed. The difference between thisexample and the embodiment described in relation to FIG. 4B, is thathere the oxygen rich layer 805, unlike analogous layer 405 in FIG. 4B,was only partially converted to the interfacial region 808. In this caseonly about 40 nm of the 150 nm of oxygen rich precursor layer 405 wasconverted to the region serving as the ion conducting layer.

FIGS. 8B and 8C show a “before and after” comparison of device, 800, ofthe invention (FIG. 8C) and the device precursor (FIG. 8B) beforemultistep thermochemical conditioning as analyzed by STEM. In thisexample, only layers 804-810, EC through CE, are depicted. The layersare numbered the same as in FIG. 8A, with a few exceptions. The dottedline in FIG. 8B is used to approximately demark the interface of EClayer 806 and oxygen rich layer 805 (this is more clear in FIG. 8C).Referring again to FIG. 8B, it appears that at least there is lithium,as indicated by 808 a, concentrated (approximately 10-15 nm thickregion) at the interface of oxygen rich layer 805 and CE layer 810.After MTCC, FIG. 8C, it is clear that interfacial region 808 has formed.

Although the foregoing invention has been described in some detail tofacilitate understanding, the described embodiments are to be consideredillustrative and not limiting. It will be apparent to one of ordinaryskill in the art that certain changes and modifications can be practicedwithin the scope of the appended claims.

1. A method of fabricating an electrochromic device, the methodcomprising: (a) forming either an electrochromic layer including anelectrochromic material or a counter electrode layer including a counterelectrode material; (b) forming an intermediate layer over theelectrochromic layer or the counter electrode layer, where theintermediate layer includes an oxygen rich form of at least one of theelectrochromic material, the counter electrode material, and anadditional material, where the additional material includes distinctelectrochromic or counter electrode material, the intermediate layer ina state that is not substantially electronically insulating; (c) formingthe other of the electrochromic layer and the counter electrode layer;and (d) converting at least a portion of the intermediate layer from thestate that is not substantially electronically insulating to a statethat is substantially electronically insulating.
 2. The method of claim1, wherein the electrochromic material is WO₃.
 3. The method of claim 1,wherein (a) comprises forming the electrochromic layer via sputteringWO₃ using a tungsten target and a first sputter gas comprising betweenabout 40% and about 80% O₂ and between about 20% Ar and about 60% Ar, toreach a thickness of between about 350 nm and about 450 nm, and heating,at least intermittently, to between about 150° C. and about 450° C.during formation of the electrochromic layer.
 4. The method of claim 3,wherein (b) comprises sputtering WO₃ using a tungsten target and asecond sputter gas comprising between about 70% and 100% O₂ and between0% Ar and about 30% Ar, to reach a thickness of between about 10 nm andabout 200 nm, without heating.
 5. The method of claim 1, furthercomprising sputtering lithium onto the intermediate layer until theblind charge is satisfied.
 6. The method of claim 1, wherein the counterelectrode layer comprises NiWO, between about 150 nm and about 300 nmthick.
 7. The method of claim 6, wherein the NiWO is substantiallyamorphous.
 8. The method of claim 1, further comprising sputteringlithium onto the counter electrode layer until the counter electrodelayer is substantially bleached.
 9. The method of claim 8, furthercomprising sputtering an additional amount of lithium, between about 5%and about 15% excess based on the quantity required to bleach thecounter electrode layer, onto the counter electrode layer.
 10. Themethod of claim 1, further comprising depositing a transparentconducting oxide layer on top of the counter electrode layer.
 11. Themethod of claim 10, wherein the transparent conducting oxide comprisesindium tin oxide.
 12. The method of claim 10, further comprising heatingthe stack formed, before or after depositing the transparent conductingoxide, at between about 150° C. and about 450° C., for between about 10minutes and about 30 minutes under Ar, and then for between about 1minute and about 15 minutes under O₂.
 13. The method of claim 1, furthercomprising heating the stack formed in air at between about 250° C. andabout 350° C., for between about 20 minutes and about 40 minutes. 14.The method of claim 1, further comprising flowing a current between theelectrochromic layer and the counter electrode layer as part of aninitial activation cycle of the electrochromic device.